An hour is no where near enough time to eat at 'Ohana and then get down to the beach. If Wishes is at 10, I wouldn't make an ADR for anything later than 7. You could easily wait 45 mins after your ADR time there. How long it takes you to eat is totally up to your family and how much they want to eat. We have had some pretty awful service there, so it has taken us a lot longer than we would have liked. I think the 3 hour buffer time will help keep you from feeling rushed. Even in the worst case that you had to wait an hour after your ADR time (it doesn't happen often but it has happened) that still gives you 2 hours to eat. Even if it takes your family 90 mins to eat, you still have a half hour to get down to the beach. I think making an ADR any later will add some unneeded stress to your night.
As for the Electric Water Pageant, it usually passes the Poly at around 9. It's nice to see if you can get there in time, but if you miss it, it's not the end of the world, IMO.